The ROQUIN family of proteins localizes to stress granules via the ROQ domain and binds target mRNAs

Abstract

Roquin is an E3 ubiquitin ligase with a poorly understood but essential role in preventing T-cell-mediated autoimmune disease and in microRNAmediated repression of inducible costimulator (Icos) mRNA. Roquin and its mammalian paralogue membrane-associated nucleic acid binding protein (MNAB) define a protein family distinguished by an 200 amino acid domain of unknown function, ROQ, that is highly conserved from mammals to invertebrates and is flanked by a RING-1 zinc finger and a CCCH zinc finger. Here we show that human, Drosophila and Caenorhabditis elegans Roquin and human MNAB localize to the cytoplasm and upon stress are concentrated in stress granules, where stalled mRNA translation complexes are stored. The ROQ domain is necessary and sufficient for localization to arsenite-induced stress granules and to induce these structures upon overexpression, and is required to trigger Icos mRNA decay. Gel-shift, SPR and footprinting studies show that an N-terminal fragment centred on the ROQ domain binds RNA from the Icos 3¢-untranslated region comprising the minimal sequence for Roquin-mediated repression, adjacent to the miR-101 sequence complementarity. These findings identify Roquin as an RNA-binding protein and establish a specific function for the ROQ protein domain in mRNA homeostasis. Abbreviations Dcp1a, decapping enzyme 1; FMRP, Fragile X mental retardation protein; G3BP, Ras-GAP SH3 domain-binding protein; GFP, green fluorescent protein; Icos, inducible costimulator; miRNA, microRNA; MNAB, membrane-associated nucleic acid binding protein; REMSA, RNA electrophoresis mobility shift assay; TIA, T-cell intracellular antigen; TIS11, TPA-induced sequence 11; TTP, tristetraprolin.

Roquin binding to target mRNAs involves a winged helix-turn-helix motif

“…As indicated by our analytical ultracentrifugation experiments, monomeric ROQUIN1 predominates at lower protein concentrations, but a concentration-dependent dimerization of Roquin has been reported by Schlundt et al 20 Since Roquin proteins accumulate in P bodies and stress granules 3,21 , it is tempting to speculate that elevated Roquin concentration at these sites might favour the formation of functional dimers.…”

Breakdown in Repression of IFN-γ mRNA Leads to Accumulation of Self-Reactive Effector CD8+ T Cells

“…Roquin was reported to bind to and repress Icos mRNA (29,30,33); prolonged Icos mRNA stability in the presence of Roquin san contributes to aberrant accumulation of CD4 + Tfh cells and lupus. The present work identifies IFN-g as a novel target of Roquin sanmediated repression.…”

Heterozygosity for Roquinsan leads to angioimmunoblastic T-cell lymphoma-like tumors in mice

“…ROQUIN has previously been shown to bind Icos mRNA through its ROQ domain and regulate inducible T-cell costimulator (ICOS) mRNA stability. [16][17][18] Mutant ROQUIN encoded by Roquin san binds Icos mRNA with higher affinity, leading to slower mRNA decay. In Roquin san/san mice, aberrant expression of ICOS on CD4 ϩ T cells contributes to an excessive accumulation of T FH cells, 15,17,19 which in turn causes lupus-like disease characterized by lymphadenopathy, splenomegaly, hypergammaglobulinemia, and the development of glomerulonephritis.…”